[78.04] ROSAT and ASCA Observations of the X-Ray Lobes of W50 Associated with the Semi-Relativistic Two-Sided Jets Source: SS433

S. Safi-Harb, H. Ogelman (UW Madison)

We report the observations of the X-ray lobes of W50
associated with the compact source SS433 known by its
semi-relativistic two-sided jets.
The eastern and western lobes were observed with
the Position Sensitive Proportional Counter (PSPC) on board ROSAT.
The lobes are symmetrically displaced east and west
of SS433, starting at \sim 15^\prime, elongated along the axis of
the jets, with an enhanced emission at \sim 35^\prime, and
extending out to \sim 40^\prime.
With ROSAT, we were able to detect diffuse emission from the
eastern lobe even further out to \sim 1^o. This emission
is coincident
with the brightest radio
filament which is thought to be the radio `hot spot' associated with the
relativistic jets from SS433
interacting with the ambient medium.
The spectrum from this region is soft,
and is either described by
a power law with a steep photon index (\Gamma \sim 4), or a thermal
bremsstrahlung with a temperature kT \sim 0.5 keV.
We also report the ASCA observations of the eastern lobe
which was detected from \sim 15^\prime
to \sim 40^\prime.
We combine the ASCA data
with the ROSAT data to get a wide coverage of the
spectra in the 0.1 -- 10 keV
energy range.
The spectra show softening with increasing distance from SS433.
Both thermal
bremsstrahlung spectra with high
temperatures (\sim 5 -- 30 keV) as well as power law spectra with hard
photon index (\Gamma \sim 1.4
-- 2) give adequate fits.
The fits are made better by adding a Gaussian line around 2 keV or by
fitting with a broken power
law, with the break occurring at \sim 2 -- 3 keV.
We discuss the thermal versus non-thermal origin of the X-rays in
correlation with the maps of W50 at other wavelengths.
We also discuss the morphology of the lobes and derive some physical
parameters for the jets based on the existing models of supersonic jets
interacting with the surrounding medium and producing a region
of `hot' shocked material.